Method for manufacturing a stiffened panel of composite material

Abstract

A process for the production of a stiffened panel made of composite material, includes the stages of depositing the fibers that constitute the panel on a rigid device ( 50 ), depositing the at least one stiffener ( 14 ), covering the unit with a sealed wall connected to the rigid device ( 50 ) on the periphery of the panel, and then polymerizing, and providing—for each stiffener ( 14 )—a rigid counter-mold in contact with the convex surface of the stiffener ( 14 ), using—for each stiffener ( 14 )—a core ( 66 ) in the form of a flexible and sealed bladder, and subjecting the interior of the bladder to pressure during polymerization for compacting the stiffener ( 14 ) and the panel.

The invention claimed is: 
     
       1. A process for the production of a stiffened panel made of composite material that comprises a panel that consists of fibers that are woven in a resin matrix, one of the surfaces of the panel being connected to at least one stiffener made of composite material in the form of a section whose cross-section comprises a non-flat central part with caps on either side in contact with the panel in an assembled state, said central part being separated from said panel to be reinforced, the process comprising:
 depositing the fibers that constitute the panel on a rigid device; 
 depositing said at least one stiffener by inserting a core between each stiffener and the panel; 
 covering a unit comprising at least the panel, the at least one stiffener and the core with a sealed wall connected to the rigid device on the periphery of the panel; and 
 polymerizing the unit by subjecting the unit to pressure, 
 wherein each stiffener is provided with a counter-mold that is rigid in contact with the convex surface of the stiffener, lateral edges of the rigid counter-mold not extending beyond lateral edges of the at least one stiffener, 
 the core in the form of a flexible and sealed bladder is used with each stiffener, 
 the interior of said bladder is subjected to gas pressure during polymerization for compacting the stiffener and the panel, and 
 for each stiffener, the bladder has at least one protruding end at the level of the protruding end of the stiffener to communicate with an outside environment of a chamber formed by at least the panel, the counter-mold, and the bladder to obtain an identical pressure in the bladder and in the outside environment of the chamber. 
 
     
     
       2. The process for the production of a stiffened panel according to  claim 1 , wherein for each stiffener, the bladder extends beyond the end of the stiffener. 
     
     
       3. The process for the production of a stiffened panel according to  claim 1 , further comprising inserting a wedge between the bladder, the stiffener, and the panel at the level of each acute angle formed by said stiffener and said panel. 
     
     
       4. The process for the production of a stiffened panel according to  claim 1 ,
 the process further comprises:
 covering one or more zones of the panel that are not covered by said at least one stiffener with at least one band having sufficient rigidity to transmit compression forces by allowing play between said at least one band and said at least one stiffener; and 
 depositing a seal such that said seal, said at least one band, and said at least one rigid counter-mold form said sealed wall, said seal being configured to have two states comprising a first malleable state during application of the seal such that the seal adapts to a profile of the lateral edges of the at least one stiffener, and a hardened state after the application of the seal to ensure the transmission of compression forces in a manner that is essentially identical to the rigid counter-molds or to the bands that are arranged on either side of said seal so as not to generate a pressure gradient. 
 
 
     
     
       5. The process for the production of a stiffened panel according to  claim 1 , wherein for each stiffener, a seal is used to ensure sealing between the rigid counter-mold and the bladder, and between the bladder and the rigid device. 
     
     
       6. The process for the production of a stiffened panel according to  claim 1 ,
 wherein a flexible and sealed wall is used to cover the panel, and 
 for each stiffener, the bladder is connected in a sealed manner to said flexible and sealed wall. 
 
     
     
       7. The process for the production of a stiffened panel according to  claim 1 , wherein the bladder is made of an expandable material. 
     
     
       8. The process for the production of a stiffened panel according to  claim 1 , wherein a mold that has served in its partial polymerization as a rigid counter-mold is used for each stiffener. 
     
     
       9. The process for the production of a stiffened panel according to  claim 1 , wherein prior to depositing the at least one stiffener, each stiffener is partially polymerized so as to be stable on a dimensional plane while allowing a final polymerization with the panel. 
     
     
       10. The process for the production of a stiffened panel according to  claim 2 ,
 further comprising inserting a wedge between the bladder, the stiffener, and the panel at the level of each acute angle formed by said stiffener and said panel. 
 
     
     
       11. The process for the production of a stiffened panel according to  claim 2 ,
 wherein a flexible and sealed wall is used to cover the panel, and 
 for each stiffener, the bladder is connected in a sealed manner to said flexible and sealed wall. 
 
     
     
       12. The process for the production of a stiffened panel according to  claim 3 ,
 wherein a flexible and sealed wall is used to cover the panel, and 
 for each stiffener, the bladder is connected in a sealed manner to said flexible and sealed wall. 
 
     
     
       13. The process for the production of a stiffened panel according to  claim 1 , wherein when the interior of the bladder is subjected to the gas pressure during polymerization, the gas pressure within the bladder becomes equal to the gas pressure in the outside environment.